Jim Cramer believes investors should identify themes and put money to work accordingly.

However, themes have a shelf life and recent price action in related stocks has led the "Mad Money" host to question whether 3 favorite themes have started to sputter out.

Following are his insights.

Theme #1 - Aerospace

Cramer says that over the past 3 months a perception has developed that there's an inventory glut in the aerospace sector. "It came about due to commentary made in the Boeing call and again in the Alcoa call," Cramer said, with the concerns sending shares of Boeing about 8% lower in 3 months.

Cramer, however, thinks the declines are ultimately an opportunity because he doesn't think the weakness will endure.

"Oil is still high," Cramer noted. "And the airlines have the money to buy new planes for fuel efficiency." Therefore, when Boeing next reports earnings, Cramer fully expects to hear that sales of new planes are robust; and ultimately assuage fears of a glut.

All told, "I think the whole group will take off after Boeing's next report," he said.

Laser222 | E+ | Getty Images

Theme #2 - Software as service cloud plays

Cramer fears this theme may be challenged due to the volume of recent IPOs.

"It's one thing when you have a handful of companies with tremendous revenue growth vying for investor attention. It's another when you have as many 25.

Although Cramer believes in the theme long-term, he fears the path of least resistance in the near-term may be lower, simply due to the laws of supply and demand.

"As far as I can tell, there are too many companies in the space and not enough dollars to chase them," Cramer said.

Theme #3 - Biotech

With Gilead down 13% in only a month and Biogen off 10% in the same period, Cramer is worried about the space broadly.

In part Cramer believes weakness is due to a strategy among institutional investors who are rotating out of these stocks and putting that money into other areas of the market that could advance more rapidly amid a global recovery.

"This group always underperforms when there a pronounced economic growth spurt is in the air, and that's just what people think we are having now," Cramer said.

It would be a mistake to conclude that Cramer is bearish on this theme, he's not. He believes that big drug approvals or big mergers could buoy this sector quickly, although, admittedly, neither has surfaced so far.

However, Cramer wouldn't be surprised if the landscape changes as soon as the second quarter.

Therefore, "If you see new approvals of promising drugs or a new wave of M&A, I'd take advantage of the current declines," Cramer said. If you're playing the theme, watch the space, carefully.